Primary open-angle glaucoma (POAG) is a chronic, slowly progressive optic neuropathy, characterized by excavation of the optic nerve head (ONH) and a distinctive pattern of visual field (VF) defects. The disease is multifactorial in origin, so that besides more extensively investigated factors oxidative stress has also been proposed as a contributing factor in the etiology of glaucomatous optic neuropathy. Oxidative stress represents a harmful state defined by the presence of pathologic levels of reactive oxygen species (ROS) relative to antioxidant defense.